Ball bearing holding structure and fan motor

A ball bearing holding structure for rotatably supporting a shaft, the ball bearing holding structure comprising:

• a bearing holder including a cylindrical holder portion into which the ball bearing is internally fitted from one side in an axial direction of the shaft, and a positioning portion provided on an other side in the axial direction of the holder portion and abutting on the ball bearing from the other side;
• and
• a mounting plate having a cylindrical mounting portion in which a portion of the holder portion is press-fitted from the other side, wherein
• an inner surface of the holder portion is provided with an adhesion surface, a relief surface and a step surface;
• wherein the adhesion surface bonded to an outer peripheral surface of the ball bearing by an adhesive, the relief surface having an inner diameter larger than an inner diameter of the adhesion surface on the one side, and the step surface connecting the adhesion surface and the relief surface, and an axial position of the step surface is a position overlapping the ball bearing in a state wherein the ball bearing is engaged to the bearing holder.